if you want to get in the water quickly just wait for the next big hurricane to hit in the gulf, theyll have every swingin d*** they can muster diving..Once your in you in, just try not to screw up.
In the States, one must head to the Gulf of Mexico after graduating dive school and hire on as a tender, spend 2 to 3 years sweating the deck and paying your dues. Most overseas companies require a diver to work Civils (inland diving work) for 2 to 3 years before they will hire you to go offshore.